I have a 2009 cannondale six5 with shimano...
I have a 2009 cannondale six5 with shimano 105flight deck shifters and ultegra rear derailleur.?Will the shimano ultegra ST-6700 dual C shifters work on this bike and be an upgrade from the 105 shifters.?
Yes, that will work. With cable routing that lies underneath your bar tape, these will give a much cleaner look than your 105's and are a nice upgrade!
Yes these will put the cable under the tape but your Brakes will not work as well unless you replace them and if you are using a Flightdeck it will not work with the new shifter.